Microfluidic devices, such as laboratories-on-a-chip, are becoming increasingly important in applications in the fields of genomics, drug screening, and other clinical applications. In conventional microfluidic devices, small volumes of liquid are maneuvered within a network of microfluidic channels to achieve a variety of chemical, physical, and/or biological processes. Microfluidic devices such as these use a system of pumps, channels, valves, and mixing elements to manipulate the fluids.
Pressure is generally required to manoeuvre a fluid within a microfluidic device. In some devices, capillary pressure or pressure generated by a pump is used to push a fluid through a network of microfluidic channels. Electrokinetic pumping is often used for this purpose but it unfortunately has some disadvantages. Firstly, electrokinetic pumping is sensitive to the physicochemical properties, such as ionic strength and pH, of the fluid. As a result, it is difficult to pump biological fluids, such as blood and urine, by this method. Secondly, electrokinetic pumping requires continuity in the fluid in the channels and, therefore, it does not work in the presence of trapped bubbles (e.g., air), and care has to be taken to ensure that the channels are free of bubbles.
An alternative pumping method is based on centrifugal force. The lab-on-a-CD platform (Haeberle et al., Lab Chip, 2007, 7, 1094-1110) relies on centrifugal pumping and has received considerable attention to date. The use of centrifugal pumps to manoeuvre fluids within microfluidic systems has been described, for example, in published United States patent application Nos. 20020097632 (Kellog et al.), 20080269077 (Lee et al.), and 20110111987 (Siegrist et al.). However, the known centrifugal pumps use rotational motors that make the pumps difficult to miniaturise to a point where they are suitable for lab-on-a-chip type applications.
There is a need for microfluidic devices that overcome one or more of the problems associated with prior art devices and/or microfluidic devices that provide alternatives to prior art devices.